Ultimate Guide to Mazda MX5 Car Battery

Mazda MX5 Car Battery
Photo by 453169

Mazda picked up the 2021 ‘Best Sports Car for Value’ in the ‘What Car’ Car of the Year Awards for the MX-5. This, alongside dozens of global awards throughout the 30-year period the car has been sold to UK customers, is a testament to its quality design. 

Now in its fourth iteration, the MX-5 has evolved subtly from its debut at the 1989 Chicago Motor Show to an affordable, reliable, and fun two-seater roadster.

With roughly 95000 samples of the car only on UK streets, the MX-5 has outsold every other performance vehicle to date. 

The sheer numbers alone have created a strong owner’s community and an aftermarket range supplying all possible parts in the likelihood that something goes wrong.

With proven reliability from the onset, owners have reported few mechanical issues, even in early NA variants from the early 90s. 

Regular maintenance isn’t an issue either, as Mazda has restarted producing OEM parts for all four generations. A bit harder to find is the original Panasonic MX-5 battery in the AGM guise (a technical marvel in the day itself).

However, newer replacement batteries are affordable, throw out a few more amps, and are accessible.  

Time to Change Old Batteries

Mazda MX5 Car Battery

If you still have a working battery from a 32-year-old NA Miata, then don’t hesitate to send your application to Guinness. Otherwise, batteries last 5 years on average and top out at 10 years max.

The car you currently have will most probably have the battery replaced a few times. With more in the way of electronics, particularly newer NC and current versions of the car, and aftermarket additions that drain quite a bit of power, like alarm systems and stereos on steroids in the older cars, newer batteries need to be put out more power. And that they do. 

That said, here’s what to look for when buying an MX-5 battery.

Battery Types

Mazda MX5 Car Battery

Mazda used sealed AGM batteries in the first two generations of the car, then shifted to wet cell lead acid batteries in the following versions. The latter has come a long way in providing more output and less maintenance. 

Prices have also gone down, but safety has increased. There’s better venting, and the likelihood of corrosive leaks is brought to a minimum.

They can also be jump-started, as opposed to AGM batteries. These, in turn, are regarded as safer and sealed options that won’t gas or leak or cause severe rusting to surrounding parts.

They can also be discharged to lower rates without damage, which is good if you use your Miata as a second car or for the odd drive on weekends. 

Owners of NA and NB cars generally steer towards AGM replacements, whereas NC and ND MX-5 owners go for newer flooded wet cell batteries.  

Capacity

This refers to the maximum amount of charge of a fully charged battery to release a stored amount of electricity over a specified time. Battery capacity is stated in Ampere hours (Ah).

Higher numbers mean the battery can maintain a constant load longer. Mazda lists the capacity requirements for each model released since 1990.  

Cold Cranking Amps

Cold Cranking Amps (CCA) is the number of amps a battery can generate at -18°C while maintaining a voltage above 7,2 Volts or what is needed to start the car.

Higher numbers mean batteries won’t struggle when it gets really cold. Another metric is Cranking Amps (CA), or the power needed to start the car at 0°C.

Generally, older Miatas require higher maximum CCAs (around 520), and newer cars (and those fitted with turbos) have higher average CCAs over a rated period.  

Size

Replacement batteries need to fit the battery bay. This isn’t an issue as batteries have become smaller while retaining the same capacity and CCAs.

The average sizes of Miata batteries are 207mm in length, 175mm in width, and 175mm in depth. Exceptions are batteries for the NC 2-litre engine (237 x 127 x 227 mm), the ND 1.5 and NA 1.6 turbo (238 x 129 x 223 mm). All Mazda batteries belong to the same size group, listed as 51. 

Positive Terminal Location

Besides being a size 51, you’ll also find the ‘R” designation. This is the positive terminal post location, being on the right. All MX-5 batteries are classed as 51R.

This is important to avoid a shot from the terminal coming into contact with the metal shell of the car or tools when the battery is replaced.

Where there are no letters, it is assumed that the positive terminal is on the left. Life Cycles, ‘Freshness,’ Maintenance Requirements, and Warranties 

Replacing your current MX-5 battery will depend on the remaining cycles or the number of times a battery can be discharged (to a safe level of 50 percent) and recharged again while driving. This can be checked by an auto electrician.  

Freshness refers to the date of manufacture, and all car batteries should be no older than 6 months at the time of purchase. This is indicated with a number (the year) and letter (the month) on the battery itself.

Battery makers also offer warranties ranging from 1 to 5 years, depending on the battery type and brand. 3 years is the norm for most batteries without going overboard with prices.  

Most batteries are marketed as maintenance-free, though for Miata owners, the rule is that AGM replacement batteries are ‘set-and-forget’ options needing virtually no maintenance, whereas wet cell batteries need periodic checks of water levels as well as the condition of the terminals and housing.  

NA/NB vs. NC/ND Miata Batteries

Mazda MX5 Car Battery

Mazda decided to put the batteries for the first two generations of the MX-5 in the boot. This made a lot of sense, as it helped with weight distribution, and the temperatures there were cooler than under the hood. And this helped with longer life cycles. 

Also, any sustained damage to the battery (leaks or explosions) was less costly than the move under the hood in NC cars from 2005 onwards.

Here the heat negatively impacted life cycles and performance, and possibly one of the reasons why Mazda went with wet batteries in larger capacities instead.

Some die-hard Mazda aficionados purchase refitting kits for the newer cars to get the battery back into the boot.  

When replacing your existing battery in the MX-5, consider any modifications and additions to electrics, as this will impact how the battery performs.

Go for batteries with a higher capacity if there are major upgrades. In unchanged cars, the benefits are obvious.

All electrics will work as they should, there’ll be no signs of low charge levels (due to faster charging rates), and there’s less to think about considering the lower maintenance needs and longer life cycles of a new battery.

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